Repair techniques for lacerated or severed tendons and ligaments ("connective cords" or "cords") vary widely depending on the nature of the injury and the particular cord affected. There are large differences in the extent to which access can be obtained in the least obtrusive manner, in the amount of cord excursion, in the surrounding environment, in the stresses to which different cords are normally subjected, and in the healing characteristics of different cords. In addition, often there is no consensus of the overall best way to repair a given cord. Examples of often injured cords having different accepted repair techniques are flexor tendons of the hand and the anterior cruciate ligament (ACL) of the knee.
For example, repair of a long flexor tendon that has been severed is typically achieved by suturing the severed tendon ends face-to-face. Historically, the joints across which the tendon acts were immobilized for from three to eight weeks to protect the tendon while it healed, because a freshly sutured tendon can withstand only a fraction of the tensile force to which a healthy tendon is subjected during normal use. Immobilization results in scarring and adhesion formation along the length of the tendon. Range of motion is adversely affected, particularly in the case of flexor tendons which normally glide smoothly through and over the unique system of tendon tunnels and pulleys of the hand. Nevertheless, it was thought that fibroblastic ingrowth was required in order for the tendon to heal, such that immobilization and the resulting decreased range of motion were considered necessary evils in order for effective healing to take place. More recently it has been discovered that flexor tendons have an intrinsic capacity to heal and that limited motion will actually expedite healing. Still, exercises must be carefully planned and carried out due to the weakness of the sutured repair. In early stages of healing, protected passive and/or restricted active exercises may be used, followed by tendon gliding and active strengthening exercises in later stages. The affected joints are most often partially immobilized to prevent inadvertent application of excess force.
In the case of an anterior cruciate ligament (connecting the bottom of the femur and the top of the tibia) the stresses resulting from applied forces are much greater, there is less interaction with surrounding tissue and bone, the excursion of the cord is less, and the healing tendencies are vastly different. Despite numerous studies, there still is no universally accepted repair procedure, and prevailing procedures are difficult and intricate. The current "standard of care" remains the reconstruction of the ACL using a bone-tendon-bone or tendon autograft (i.e., harvested from the patient). However, there are multiple problems with autografting: (1) the intact ACL possesses important mechanoreceptive and proprioceptive capabilities, and graft reconstruction sacrifices these capabilities; (2) autografting involves considerable donor site morbidity; (3) to avoid donor site morbidity, occasionally a cadaveric graft is used, which carries the risk of disease transmission.
These problems with ACL reconstruction have led to renewed interest in primary repair of the ACL. In the case of primary repair without augmentation, small bores are drilled in the adjacent bones approximately at the anatomically correct sites for normal connection of the ACL. Multiple loops of suture are used for reconnecting the ligamentous stumps to the bone. Several loops of permanent suture can provide an initial strong repair. However, over time the strength of the repaired ACL often decreases, which is indicative of a failure in the healing process. In general, it is now accepted that healing tendencies of the intra-articular ACL are poor, particularly when compared to the neighboring extra-articular medial collateral ligament which heals readily.
Failure or long-term weakening of ACL primary repair has led to techniques for "augmenting" a primary repair. These can involve suturing biological material, such as a section of patellar tendon, across a repair site, and the use of artificial augmenting strips or sheaths which typically have been flexible and fibrous in the hope that healing of the ACL will be promoted, rather than being inhibited by, the close proximity of an artificial "shield." Strips or bands of Dacron, polyethylene or carbon fiber have had their opposite ends stapled or otherwise anchored to the adjacent bones to provide the primary or secondary support for the "healing" ACL.